Commutator.



PATENTED DEC. 4, 19 06.

S. S. SEYFBRT. GOMMUTAT OR.

APPLICATION FILED 133.20, 1905.

3 SHEETS-SHEET l.

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'PATENTED 1130.4, 1906.

S. S. SEYFBRT. COMMUTATOR.

APPLICATION FILED rm. 20, 1905.

3 SHEETS-SHEET 2.

S. S. SEYFERT.

GOMMUTATOR.

AP PLIOATION FILED FEB. 20, 1905.

3 SHEETS-SHEET 3.

PATEVNTED DEC. 4, 1906.

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UNITED STATES PATENT OFFIOE.

STANLEY S. SEYFERT, OF SOUTH BETHLEHEM, PENNSYLVANIA, ASSIGNOR OFONE-HALF TO WILLIAM S. FRANKLIN, OF SOUTH BETHLEHEM,

PENNSYLVANIA.

'COMMUTATIQR.

Specification of Letters Patent.

Patented. Dec. 4, 1906.

, Application filed February 20, 1905. Serial No. 246.587.

and a longitudinal sectional view of a corn mutator embodying myinvention, and Figs. 5 and 6 are views similar to Figs. 4 and 5 ofanother-embodiment of my invention.

The object of my invention has been to provide a commutator by whichcurrents of high voltages can be commutated without sparking, suchcommutator, while especially valuable in alternating-current motors,being I adapted for use in commutating other ourby the brushes is theseat of a comparatively rents than those in a motor; and to such ends myinvention consists in the commutator hereinafter specified.

The, commutators of all single-phase motors at present devised otherthan that here-- inafter described are, so far as I am aware, soconstructed as to be subject to such serious sparking at the brushes asto prevent the use of currents ateconomical voltages. The main cause ofsparking is the fact that the coil of the armature which isshort-circuited high electromotive force induced in it b y transformeraction, because of the alternating character of the exciting-field. Suchcoil is perpendicular to the lines of force and is therefore in positionto embrace the largest possible number of lines of force, so that theinductive action therein is the strongest possible in any coil of thearmature.

Such coil being short-circuited by the brushes, large currents will flowin it, because of the comparatively low resistance of the short-circuitpath. These currents causeheating of the brush-contacts, a loss ofpower, and sparks when the short-circuit is broken. The object of thecommutator about to be described.

is to reduce such short-circuit currents, and thus to save power andminimize the destructive heating and sparking at the commutator.

The commutator is diagrammatically illustrated in Fig. 1, in which thecoils on sections A A, &c., of the armature-winding are connected byleads B B, &c., which would ordinarily pass directlyto thecommutator-segments, but which in accordance with my 1n-' vention areconnected with choke-coils O C, &c., and D D, &c., in airs, thechoke-coils being connected by lea s E E, &c., with thecommutator-segments F F, &c. The choke or inductance coils C &c. and D,&c. are so arranged that when alternating current flows upward ordownward in both coils of a pair their magnetizing action will be equaland 01pposite, and no impedance will be offered to t passage of thecurrent. If, however, current tries to flow up one coil and down theadjacent coil of a given pair, such as up one coil C and down theadjacent coil D, the magnetizing action of the two coils will be in thesame direction, and a heavy impedancewill be opposed to such current.For this urpose two choke-coils may be wound on t e same iron core ormagnetic circuit, and the termi-. nals are connected so as to obtain theefiect above mentioned. Thus coils C and D are linked with-one 'ma neticcircuit, while coils C and D are linke with another magnetic circuit,and soon. In the operation of my commutator, as illustrated in Fig. 1,at the instant when the brush G bridges over the segments F and F iftransformer electromotive forces are introduced in coil A they will tendto produce corresponding currents in the short-circuit, which may beassumed to be in the direction of the dotted arrow below such coil at agiven instant. Then current will tend to flow down the lead 13, downcoil C ,-dOWI1 lead E through commutator-segment F through the brush Gto the segment F, and thence through lead E and 0011 D andback to thearmature-coil by lead B It will thus be seen that this short circuitcurrent must flow down coil C and up coil D but, as before stated, whenthis takes place the coils interpose a lar e choking ef: feet, and hencethe short-circuit current will be kept down on account of the inductanceof the coils C and D 'While the coils C and D will largely prevent theflow of current formed by transformer action in the short,- circuitedcoil, they do not ofier any objec- 'tionable resistance to the flow ofthe main armature-current, because such current will pass through bothof such coils in the same direction-that is, upward or downward, so thattheir magnetizing action will be coun' terbalanced. No substantialportion of the short-circuit current above described can flow in theisolated coils D and 0 because their magnetizing action is notcounterbal- 'anced b any 0 posite magnetizing action,

and suc coils t erefore offer their full impedance to the passa e ofcurrent.

Continuing now t e theory of my commutator, if a number ofcommutator-segments between a set of positive and negative brushes be,say, fifty, then each of the chokecoils, as above described, will beactuallycarrying half of the armature-current for only about onetwenty-fifth of the time. If be half the armature-current (assumingbipolar, simplex, la -winding) and R be the resistance of a cho e-,coil, then while current is actually flowing the rate ofheat-generation in the coil under consideration is R(%-) but since thisoccurs only one tw'entyfifth of the time the actual rate of heatgeneration may be twenty-five times as great while it occurs and stillnot heat the choke-coils faster than the armature is being heatedthatis, the resistance of the choke-coil may be twenty-five times as greatas would be permissible if the current were flowing all the time, or thecross-section of the conductors of the choke-coils may be made onetwentyfifth of the cross-section of the armatureconductors, keepingtheir length the same. The same eflect can be obtained by multiplyin thelength of the choke-coils by five and ecreasing their cross-section toonefifth, thus givin approximately five times as many turns andtwenty-five times as much an inductance in a given space: Thus ithappens that the resistance of two of these 0110 -coils in serieswill beconsiderable, and this still further tends to reduce the shortcircuitcurrent. spect to the main-armature current, the two coils C and D, Fig.1, are in parallel and their combinedresistance will still be small ascom ared to the total armature-resistance. thus obtain the efiect of theintroduction of ohmic resistance in the short-circuit formed by thebridging of two commutator-segments by a brush; but I do sowithout'requiring the use of high-resistance material, inasmuch as mychoke-coils may be of good copper wire, but of greatly diminishedcross-section .and greater length as compared with the conductor of thearmature.

thus obtain the double'object of introducing high resistance in theshort-circuit, together with the choking effect of'the coils thusformed, without introducing an objectionable bulk of material. If theinductancecoils were formed of material of high ohmic I resistance and asufficient length were used .-commutator-segm'ents.

On the other hand, with reto produce the desired inductive effect, abulk would result that would be a serious objection.

The choke-coils may be of copper strap insulated with asbestos, so as tobe thoroughly heat-proof.

It will be seen that with-my commutator the simplest form ofarmature-winding may be used and no special form of brushes is required.A higher voltage per segment can also be used, giving either a higherline voltage or a lower ratio of transformation. j

The commutator may be varied in form. In Fig. 2 is illustrateddiagrammatically an arrangement of commutator on the principle of thatillustrated in Fig. 1;, in which compactness and economy of iron iseffected.

The armature coils H H, &c., are, as before,

connected by leads I I, &c., with chokecoils K K, &c., and L L, &c., thelatter being wound on the multiple iron core M. This core may consist ofa ring or band of iron laminations with openings punched in the same forreceiving the coils. The coils are connected by leads N N, &c., withcommutator-segments O O, &c., that coact with the brush P.

In Figs. 3 and 4 is illustrated a commutator constructed according tothe arrangement illustrated in Fig. 2 and applied to a railway-motor.

The case Q .is provided with a cover R, in which is formed a bearing forthe shaft S. The commutator-segments T are held between two annularplates U and U, respectively, the plates having flanges a and a,respectively, which bear against the inner surface of the motor-casing.The plates are clamped against opposite sides of the commutator-segmentsby bolts V, the plates having V-shape ribs W, which. engage complementalrecesses formed in the The ring of commutator-segments is thus madestationary. The inner surface of the segment-ring is used for contactwith the brushes X, and the latter are mounted in brush-holders Y, having stems y, that are secured by .nuts to a carrier Z, that is mountedon and rotates with the shaft. The brush-holders are insulated from thecarrier and the connections with the brushes are made to thebrushholders. Between the plates U and U the choke-coils A and theircore B are mounted. The core is annular in form, as illustrated in Fig.4, and it is preferably laminated. The core is provided with slotsparallel to but removed from its outer periphery, and the choke-coilsare wound through such slots. The coils are, as indicated in Fig. 2,connected with the commutator-segments and with the armature-coils. Thecoils are most conveniently formed of strap conductor, althou h wire canbe used.-

'lnFigs. 5 and'6 is illustrated a commutator constructed according tothe arrange- The choke-coils are connected by leads U" with thearmature-coils. The electrical ac- 'tion of the commutator illustratedin Figs.

and 6 is the same as that illustrated in Figs.

3 and 4.

My commutator has, among others, the

following advantages: r

The commutator, being stationary, may

be constructed very rigidly and is better suited to radiate heat thanthe ordinary commutator. This is an important factor, as the commutatorof an alternating-current motor has an especial tendency to heat onaccount of the short-circuited current under the brushes. The stationarycommutator allows of a great subdivision of poles, and hence lesstrouble with short-circuit voltages under the brushes (because the fluxper pole need notbe-as great; and hence less voltage produced per coil).

It being practicable to use a material of good conductivity, such ascopper, in the chokecoils and still to obtain the desired resistance,the cost is less than if it were necessary, as heretofore, to use amaterial of poor conductivity, such as German silver.

The commutator-segment rin being eX- ternal ermits the core of the choe-coils and the coi s themselves to be as large as desired.

The use of an external segment-ring affords room within the ring for.the shaftbearing, thus saving the space on the shaft which would betaken up if the bearing were beyond the side face of the segment-ring'as heretofore constructed. This is an important consideration Where thespace is limited,

' as in railway-motors.

It is obvious that various changes can be made in the above-illustratedconstruction which will be within the scope of my invention.

/ Having thus described my invention, what I claim is a v 1. In anelectrical device, the combination of an armature comprising coils, acommutator comprising segments, leads connecting said coils andsegments, and oppositely act ing inductances ineach lead, theinductances of o posite signs in different leads being situate in thesame magnetic circuit.

2. In an electrical device, the combination of an armature comprisingcoils, a commu tator comprising segments,,leads connecting said coilsand segments, and oppositely-acting inductances in each lead, theinductances of opposite signs in difierent leads being situated in thesame magnetic circuit, said 'in, ductances being composed of material ofhigh conductivity.

3. In an electrical device, the combination of an armature comprisingcoils, and a commutator comprising segments, of inductive resistanceconnected in the leads, assing from said coils to said segments, sairesistance being active as against current tending to form byshort-circuiting a coil and being passive as against the mainarmature-current.

4. In an electrical device, the combination of an armature comprisingcoils, a commutator comprising segments, and ohmic and. inductiveresistance connected in the leads passing from said coils to saidsegments, said resistance being of high conductivity, being active asagainst current tending to form by short-circuiting a coil, and beingpassive as against the main armature-current.

5. In an electrical device, the combination of an armature comprisingcoils, a commutator com rising segments, and oppositelywound inuctance-coils connected in each lead from said armature-coils to saidsegments, oppositely-wound'coils of adjacent leads having a commonmagnetic circuit.

6. In an electrical device, the combination of-an armature comprisingcoils, a commutator comprising segments, and oppositely woundinductance-coils connected in each lead between said armature-coils andsaid segments, oppositely-Wound coils of adjacent leads having a commoncore and a common magnetic circuit, all of said cores forming parts of asingle mass of iron. 4

7. In an electrical device, the combination of an armature comprisingcoils, a commusteel having slots formed parallel to, but removed from,its periphery, said coils being wound through said slots.

8. In an electrical device, the combination of an armature comprisingcoils, a commutator comprising segments, and oppositelywoundinductance-coils connected in pairs in the leads passing from said coilsto said segments, each of said pairs of coils being wound upon a corecommon to said pair, all of said cores forming parts of a single mass ofiron or;

steel, said mass comprising a r ng or rings 'of' steel having slotsformed parallel to, but removed from, its periphery, said coils being-Wound through said slots, and over said periphery. v

9. In an electrical device, thecombination' of an armature comprisingcoils, a commutator com rising segments, and oppositelywoundinuctance-coils connected in pairs 1n.

the leads passing from said coils to said segments, each of said pairsof coils being Wound upona core common to said pair, all oi-said coresforrning parts of a single mass of iron or steel, said. mass comprisinga ring or rings of steel having slots formed parallel to, but removedfrom, its periphery, said coils being Wound through said slots and oversaid periphery, said coils being formed of bands of metal of highconductivity.

10. In an electrical device, the combination of an armature comprisingcoils, a commutator comprising segments, and. oppositely-Woundinductance-coils connected in pairs in the leads passing from said coilsto said segments, each of said pairs oi coils hesenses ing Wound upon acore common to.said pair, all of said cores forming parts of a singlemass of iron or steel, said mass comprising a ring or rings of steelhaving slots formed parallel to, but removed from, its periphery, saidcoils being wound through said slots and over said periphery, said coilsbeing formed of bands of metal of high conductivity, said bands beinginsulated with non-combustible material.

In testimony that I claim the foregoing I have hereunto set my hand.

STANLEY, S. SEYFERT. Witnesses:

NILLiAM S. FRANKLIN, A. L. Core.

